The present invention relates generally to a system for transporting bulk materials via a railway and for discharging the bulk materials at an unloading site, and more particularly to a railroad car and container for transporting bulk materials and a system for discharging the materials from the container.
At present, the only remaining viable mining industries in the United States are the coal and aggregate industries, accounting for 45 percent and 40 percent of US mines, respectively. The coal industry produces about 1.2 billion tons/year, of which about 75 per cent is shipped to market via railways. Coal sells for about $5/ton FOB at the mine in the western United States and about $20/ton in the eastern United States. However, delivered costs have been reported at about $15-$30/ton, with the western railroads receiving $0.012-$0.016/ton mile freight rates. In comparison, the aggregate industry produces about 3 billion tons/year, of which only about 6 percent is shipped to market via railways. Aggregate sells at a mine for the same average price as Wyoming coal, around $5/ton. The aggregate products are typically shipped 25-200 miles to market at $0.08-$0.14/ton mile or $2-$28/ton by trucking. Average western United States railroad non-coal mineral freight rates of around $0.0258/ton mile have been reported. Thus, delivery of aggregate via railways could compare quite favorably with delivery by truck.
These statistics suggest that the railroads are servicing the coal industry far more effectively than the aggregate industry. Indeed, the railroad industry has shown limited interest in the aggregate industry due to a perception that transporting aggregate would be less profitable than transporting coal because aggregate is shipped for shorter distances and has a lower delivered price than coal. As a result, railroads charge higher aggregate freight rates, and aggregate shippers are uncertain as to how to use railroads effectively.
In particular, the lack of an efficient railroad car for transporting aggregate and the lack of an efficient way to unload or discharge aggregate from existing cars are considered to be major deterrents to the increased use of railroads for shipping aggregate. At present, the average turnaround time for railroad cars known in the art is about 21 days. However, a viable large volume viable commercial system transporting materials over distances up to about 200 miles would need to have turnaround times of one to three days Although 1-3 day turnaround times are achievable with some existing equipment, such short times have been achieved only for limited size material and with large capital equipment and operating costs.
In one fast and effective system for transporting and dumping coal, the coal is shipped in car unit trains pulled by several high horse power locomotives. These trains may include 100 or more railroad cars, with each car carrying about 100-115 tons. Commonly, aluminum rotary dump cars are used. These cars are equipped with special swiveling couplers and are unloaded by being turned upside down. The unloading facilities used with these cars include rotary dumps that engage the car and track to rotate them on an axis through the couplers. Typically, large concrete silos are used to load such trains. The locomotives cost over $1.5 million each, the rotary dump cars cost over $50,000 each, and the construction costs for the rotary dumps and loading silos are several millions of dollars.
However, rotary dump systems such as those used for coal are much too costly for aggregate applications. Further, most existing cars designed for hauling coal are not suitable for hauling aggregate due to the significantly greater density of aggregate, approximately twice the density of coal Crushed coal has a density between about 40 and about 54 pounds/cubic foot, while crushed rock has a density of between about 94 and 100 pounds/cubic foot.
A variety of systems and types of railroad cars have been used for transporting bulk materials such as aggregate. The predominant type of car is an open top bottom dump hopper car, constructed of steel. Because these cars are emptied by dumping from the bottom, expensive permanent facilities are required beneath the railroad tracks to receive the dumped bulk materials. Typically, these facilities include large, rail-supporting I beams suspended over permanent steel hoppers, all of which are mounted in thick, high-strength concrete foundations about 16-32 feet beneath the railroad tracks. Once built, such facilities are never moved unless closed down, and then only the hopper can be salvaged. The concrete foundation must be abandoned or destroyed. Further, unloading smaller sized or wet bulk materials, which pack during transport, generally requires a device that vibrates the cars to dislodge and discharge the loads.
Numerous car designs have been proposed with different car lengths, different numbers of hopper doors, and using different types of doors in attempts to improve discharge rates and provide a system more compatible with using railroads instead of trucks for transport. One of the current predominant business strategies is to alter old steel cars designed for transporting coal by cutting a section out of the middle of the car to reduce the maximum cargo volume, along with decreasing the number of doors and making the slopes of the floor sheets steeper at the ends of the cars. These car modifications increase dumping efficiencies and train capacity by reducing the number of doors handled by employees, allowing rock to dump faster due to the steeper angles of the floor sheets at the ends, and creating shorter cars that fit on shorter sidings.
However, the hopper doors on existing cars generally do not accommodate material larger than about six inches in diameter, and often the maximum acceptable product diameter is less than three to four inches. These cars cannot handle many aggregate industry products that have larger particle sizes, including some items, such as rip rap and decorative rock with diameters as large as two to four feet.
Other systems have been proposed and used to transport and dump aggregate materials. For example, the Car Topper-Herzog method uses a patented loader that sits on top of the sides of a gondola type car and digs material out of the car. The Difco type car and variations have a hinged body built into the car. An air or hydraulic ram system, incorporated into the car, is used to tilt the car body on the hinge for unloading to either side. In the slot or trough train, specialty gondola cars have doors at either end of each car in the train and are designed to allow a loader to drive through each car and on to the next car, digging out the material from the car floor and dumping the load along the side of the car. The dump train, developed by Georgetown Railroad, includes 16-18 open top hopper cars with a belt running through the cars to the end of the train, conveying material through the train cars to a special discharge car with a 50-foot conveyor boom to discharge anywhere on either side of the end of the train. In other applications, a belt is placed above the rail and beneath the car""s door to transport dumped material away from the car and tracks.
Other major bulk materials shipped by rail include iron ore and garbage. Iron ore is usually unloaded in a manner similar to that of the first method, with dumping from open top bottom-dumping cars. Dumping occurs from a unit train onto huge piers extending out into the Great Lakes with large chutes directed into the holds of large lake vessels. However, due to the high density of the ore, 165 pounds per cubic foot, much smaller cars are required, and these cars have insufficient cubic foot capacity for practical use in transporting lower density bulk materials. At present, rail transport is used on a limited basis for garbage in ISO sized containers and specially modified box cars. The ISO sized containers, loaded with garbage, are delivered to a rail yard by truck, transported by rail to a destination, lifted off of the delivering railroad car, and usually placed on a truck for transportation to a receiving disposal pit, where the containers are tipped up from each truck and dumped from the end of the container.
The advantages and disadvantages of these existing systems for transporting and unloading aggregate materials are compared in Table I. All of the existing systems suffer from one or more of the following shortcomings:
high cost of implementation
low capacity per train
slow unloading
labor intensive unloading
undesirable longitudinal stockpiles
inability to handle larger diameter materials
Despite the fact that the US aggregate industry has an annual sales volume of 3,000,000,000 tons/year, making it more attractive than any other bulk freight commodity in the US or the world, there is a need for an improved system for railway transport of aggregate materials.
It is an object of the present invention to provide a system for transporting and unloading bulk materials, particularly materials having a density higher than that of coal but low enough for transportation in large volumes using existing railroad infrastructure.
It is another object of the present invention to provide a more economical system than is presently available for transporting and unloading bulk materials such as aggregate.
It is yet another object of the present invention to provide a system for transporting bulk materials that can carry and rapidly dump nearly any commercial size rock or bulk material.
It is a further object of the present invention to provide a system for transporting bulk materials that can handle a variety of particle sizes without the need for vibrating or shaking cars to unload packed materials.
It is yet a further object of the present invention to provide a system for transporting and unloading bulk materials that uses unit trains.
It is a still further object of the present invention to provide a system for transporting and unloading bulk materials with containers having improved rock holding and unloading capabilities, including the ability to rapidly move material of any size, unload the material rapidly, and carry the unloaded material rapidly away from the site of unloading.
It is still another object of the present invention to provide a system for transporting and unloading bulk materials that can operate with a minimum of labor.
One embodiment of the present invention comprises a system for transporting and unloading bulk materials. The system comprises at least one railroad car and a container for the bulk materials. The container comprises a bottom member having opposing first and second longitudinal sides and opposing ends, end walls secured to the ends of the bottom member, one side wall secured to the first longitudinal side of the bottom member and to the end walls, a structural support member connecting the end walls at or near the top of the end walls on the side opposing the side wall, and at least one bottom-opening door member hingedly attached to the structural support member and releasably engageable with the second longitudinal side of the bottom member. In addition, the system comprises mounting means for retaining or releasably attaching the container to the car adjacent the ends of the bottom or side member and maintaining the container on the car while the car is traveling. The mounting means provides for rotation of the container relative to the car along the second longitudinal side of the bottom member. The system also comprises tilting means for engaging the container at the side wall or adjacent the first longitudinal edge of the bottom member and a hopper assembly for receiving bulk materials unloaded from the container. The tilting means is located adjacent a railroad track upon which the car and container can travel, and the take away hopper assembly is located adjacent the railroad track in juxtaposition with the tilting means.
The car may be adapted for carrying the secured containers when loaded with a bulk material, and its bottom member may be substantially planar. The bottom member, end walls, side walls, and door member may be capable of carrying a selected bulk material without being deformed by forces exerted on the container by the bulk material. The door member of the container may form an entire wall of the container. Each end of the container may be secured on top of a bolster positioned over wheel/axle truck assemblies of the car. The container may have standard ISO dimensions, and the car may be dimensioned to receive such a standard ISO dimensioned container. Also, a plurality of containers may be secured to one car, or a plurality of containers may each be releasably secured to a different car.
Preferably, the tilting means is located on the opposite side of the railroad track from the hopper. The tilting means may comprise one or more hoists or one or more rams, and it may be operative to prevent the container from pivoting so far on the hinge that the car becomes imbalanced. The system may further comprise jacks for engaging the car on the hopper side and preventing the car from tipping with the container.
Another embodiment of the present invention comprises a container for transporting and unloading bulk materials via a railroad. The container comprises a bottom member having opposing first and second longitudinal sides and opposing ends; end walls secured to the ends of the bottom member; one side wall secured to the first longitudinal side of the bottom member and to the end walls; a structural support member connecting the end walls at or near the top of the end walls on the side opposing the side wall; and at least one bottom-opening door member hingedly attached to the structural support member and releasably engageable with the second longitudinal side of the bottom member.
The container may further comprise attachment means for releasably attaching the container to the car adjacent the ends of the bottom member, wherein the attachment means provides a hinge for rotating the container relative to the car along the second longitudinal side. It also may comprise means for engagement by a tilting device on the side wall or the bottom member. The container door may be releasably engageable with the second longitudinal side of the bottom member.
Another embodiment of the present invention comprises a ram assembly for tilting a railroad container on a railroad car. The assembly comprises a frame for supporting at least one ram; and at least one telescoping ram having a head adapted for engagement with a railroad container mounted on a railroad car. The ram assembly is operable from a position adjacent a set of railroad tracks to tilt the railroad container on the railroad car. The ram assembly may further comprise a hydraulic system for operating the ram or rams. The ram assembly may be portable.
Yet another embodiment of the present invention comprises a method for transporting and unloading bulk materials. The method comprises the steps of positioning a railroad car adjacent a tilting means and a hopper for receiving unloaded bulk materials. A container at least partially filled with a bulk material is releasably mounted on the car, and the container comprises a bottom member having opposing first and second longitudinal sides and opposing ends, the end walls secured to the ends of the bottom member, one side wall secured to the first longitudinal side of the bottom member and to the end walls, a structural support member connecting the end walls at or near the top of the end walls on the side opposing the side wall, and at least one bottom-opening door member hingedly attached to the structural support member and releasably engageable with the second longitudinal side of the bottom member. In an additional step, the tilting device is engaged with the container. Another step comprises disengaging the door member from the second side of the bottom member to allow the door to swing open by pivoting about the hinged attachment, thereby allowing a portion of the bulk material to push the door open and fall into the hopper. In yet another step, the container is tilted along the first longitudinal side to cause the container to pivot along the base of the second longitudinal side, thereby causing the remainder of the bulk material to fall into the hopper. Additional steps include lowering the container back onto the car and disengaging the tilting device from the container, re-securing the container to the car; and re-engaging the door to the second side of the container bottom.
In the method, the securing step may further comprise pre-selecting an orientation for the container on the car to allow subsequent unloading on a pre-selected side of the car. The tilting step may use a portable tilting device, and the tilting device may be selected from hoists and rams. Also, the hopper may be portable.
Optionally, there may be a plurality of railroad cars carrying containers of bulk material; and the steps of the method may be repeated with each of the cars. Also optionally, the method may include additional steps of obtaining a container for bulk materials; securing the container to a railroad car in a manner that the first longitudinal side of the container is releasable from the railroad car and the container is pivotable on an axis along the second side of the bottom member; engaging the door member with the second longitudinal side of the bottom member to prevent the door member from opening; loading a bulk material into the container; and transporting the loaded railroad car and container to a position on railroad tracks adjacent the tilting means and the hopper.